1. Field of the Invention
The present invention is a process for producing a sulfonate of an unsaturated fatty acid ester. More specifically, it relates to a process for producing a sulfonate of an unsaturated fatty acid ester at a high conversion without causing discoloration by using, as a reacting solvent, a saturated fatty acid ester. Futhermore, it relates to a process for producing a sulfonate of an unsaturated fatty acid ester at a high recovery efficiency and with good workability.
2. Description of the Prior Art
Sulfonation of saturated fatty acid esters can be effected by known methods, as disclosed in, for example, Japanese Examined Patent Publication (Kokoku) Nos. 39-20842, 39-28635, and 41-965. The sulfonates can be neutralized and hydrolyzed to obtain the desired sulfonates having a pale tone color at a high conversion. However, when the above-mentioned sulfonation methods are applied to sulfonation of an unsaturated fatty acid ester, the desired sulfonated products cannot be obtained at a high conversion. If a mole ratio of a sulfonating agent such as SO.sub.3 to an unsaturated fatty acid ester is increased, not only is the desired high conversion not necessarily obtained, but also the color of the resultant sulfonated product is remarkably decreased due to the formation of polysulfonates having 2 or more sulfonic acid groups therein.
Sulfonates of unsaturated fatty acid esters, advantageously provide detergent compositions having an excellent foaming power, detergent power, and penetrating power as well as a good rinsing property by formulating the sulfonates of unsaturated fatty acid esters with sulfonates of saturated fatty acid esters into the detergent compositions. Recently, sulfonates of unsaturated fatty acid esters have been especially noted as a surfactant. Consequently, there is a demand that sulfonates of unsaturated fatty acid esters having a pale tone color suitable for use in a detergent composition be produced at a high conversion.